The invention relates to an arrangement for the directional transmission of light in symbol indicator systems which are to be visibly effective over comparatively great distances and in which the symbols are formed by dots, of a dot matrix, which form the end termination of respective light conductors of a light conductor bundle, in which the opposite ends of such light conductors may be illuminated by light sources, particularly for use as supplemental or additional indicators in the railroad signalling field.
In such railroad signalling field, so-called additional or supplemental indicators are utilized, over and above the common optical light signals, whereby the desired signal representation is achieved by means of different light colors or different light-dot combinations. It is possible by means of such supplemental indicators to represent desired specific alphanumeric symbols which can be recognized from a train even over relatively great distances. Each supplemental indicator comprises a number of light dots which are distributed over an indicator board of the supplemental indicator, in a matrix configuration, i.e. a predetermined pattern or grid with the various light dots being illuminated in dependence upon the symbol to be depicted. Suitable signal lamps, for example, may serve as the light source for the illumination.
It is already known in the art, for example from German Auslegungsschrift No. 2,437,580, to effect the desired illumination of the matrix dots by means of respective ends of multi-light-conductor bundles whose grouped opposite ends may be illuminated by suitable light sources. In order to improve the symbol visibility over fairly great distances, particularly under poor visibility conditions, it is known in the art to associate specific optical systems with the individual matrix dots, whereby the optical systems are provided with a frustrum shape, intended to radiate as large a portion as possible of the light, received from the light conductors, in the direction toward a distant observer.
While this known type of signal indicator system possesses the advantage of relatively good recognizability, even over fairly large distances, it is subject to the drawback that the individual light dots by which the symbols are depicted, can be recognized only within a very specific narrow lateral angle, corresponding to the particular angle of the optical system disposed in front of the light conductors. Even relatively minor lateral positional deviations of an observer from the optical axes of the projecting system, produces an extremely strong impairment, at the location of observation, of the recognizability of the symbol which is sought to be depicted. Such axial shifts between observer and optical projection system may result, for example, from the track configuration ahead of the indicator involved, as well as from the incorrect locating or directional orientation of such indicators.